An early French digit cipher: deciphering a letter from the King of France to the Duke of Nevers (1592)

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dc.contributor.authorDesenclos, Camille
dc.contributor.authorLasry, George
dc.contributor.editorWaldispühl, Michelle
dc.contributor.editorMegyesi, Beáta
dc.date.accessioned2024-05-08T10:58:54Z
dc.date.available2024-05-08T10:58:54Z
dc.date.issued2024
dc.description.abstractWe deciphered a single letter written in 1592 by Henry IV, King of France, to Louis de Gonzague, Duke of Nevers, held in the Bibliothèque Nationale de France (BnF). The ciphertext mostly consists of contiguous digits, and demonstrates an early use of digit ciphers in 16th-century France. In this letter, Henri IV exposes some parts of his current military strategy against the Catholic League. After deciphering the letter, we were able to locate the original cipher table in another BnF manuscript, illustrating how codebreaking may assist historical research both to reconstruct the content of encrypted letters and to identify anonymous cipher tables.
dc.identifier.issn1736-6305
dc.identifier.urihttps://hdl.handle.net/10062/98465
dc.identifier.urihttps://doi.org/10.58009/aere-perennius0090
dc.language.isoen
dc.publisherTartu University Library
dc.relation.ispartofseriesNEALT Proceedings Series 53
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjecthomophonic ciphers
dc.subjectdigit ciphers
dc.subjectcontinuous digit ciphers
dc.subjectFrench cipher
dc.subjectKing Henry IV
dc.subjectthe Duke of Nevers
dc.subjectthe French Wars of Religion
dc.subjectBnF
dc.titleAn early French digit cipher: deciphering a letter from the King of France to the Duke of Nevers (1592)
dc.typeArticle

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Proceedings of the 7th International Conference on Historical Cryptology (HistoCrypt 2024)